Booster is a simple tool to help you release memory (RAM) space when you find your Android smartphone laggy. It can calculate the percentage of RAM being used in total and how much being used by individual apps.

Go to AirDroid app > tap Booster:

Select the app or service you don’t need now, tap Boost to free the memory and speed up your mobile:

You can add some specific apps that you wish to keep to Process whitelist: